In the construction of modern structures such as buildings and bridges, generally, beams and columns are arranged and fastened together using known engineering principles and practices to form the skeletal backbone of the intended structure. The arrangement of the beams, also referred to as girders, and/or columns is carefully designed to ensure that the framework of beams and columns is able to support the stresses, strains, and loads contemplated for the intended use of the bridge, building, or other structures.
The beams and columns used in buildings are, generally, one piece, uniform steel rolled sections; and each beam and/or column, generally, includes two elongated rectangular flanges disposed in a parallel arrangement; and a web disposed centrally between the two facing surfaces of the flanges along the length of the sections. The column is, generally, longitudinally or vertically aligned in a structural frame. A beam is typically referred to as a girder when it is latitudinally or horizontally aligned in the frame of a structure. The beam and/or column are able to withstand a strongest load when the load is applied to the outer surface of one of the flanges and toward the web.
When a girder is used as a beam, the web extends vertically between an upper and lower flange to allow the upper flange surface to face and directly support the floor or roof above it. The flanges at the end of the beam are welded and/or bolted to the outer surface of a column flange. The steel frame is erected floor by floor. Each piece of structural steel, including each beam and column, is preferably prefabricated in a factory according to a predetermined size, shape, and strength specifications. Each steel beam and column is then, generally, marked for erection in the structure in the building frame. When the steel beam and columns for a floor are in a place, they are braced, checked for alignment, and then connected using conventional riveting, welding, or bolting techniques.
Making engineering assessments of loads utilizes application of current design methodologies. These assessments, are generally compounded in complexity when considering impact on loads due to seismic events and/or determining the stresses and strains caused by these loads in structures located in areas that are prone to earthquakes. It is well known that during an earthquake, the dynamic horizontal and dynamic vertical inertia loads and stresses imposed upon a building may have the most impact on the connections of the beams to columns which are supposed to constitute the earthquake damage resistant frame. Under the high loading and stress conditions during a large earthquake, or from repeated exposure to milder earthquakes, the connections between the beams and columns may fail, possibly resulting in the collapse of the structure and leading to loss of life.
While suitable for use under normal occupational loads and stresses, often these connections may not be able to withstand larger loads and stresses experienced during an earthquake. Even if these loads and stresses do not cause damage in the structure, they often cause changes in the physical properties of the connections that may be severe enough to deteriorate the structure strength. There is, therefore, a need for beam and column connections that improve the strength of steel frame structures against great unpredictable loads including loads caused by such events as earthquakes.